You have to appreciate how much effort goes into creating this piece of software, everything from the app to the changelog looks like a work of art.

I think your definition of open source is a bit corrupted, and skewed towards expecting people to work for free in perpetuity. The Lunar repository contains open source code, and you should not expect it to compile without errors, nor should you expect maintainers to accept patches.

They don't owe you anything, and they already gave you more than most developers will do through their entire careers. I think it's perfectly understandable that the developer tries to find ways to make such a high quality project sustainable and profitable in the long term, and it won't help anyone to diss on them.